2. healthy children (1 - 5 years)and adults (18-45 years) both males and females living in the Mirpur field site, who are not currently enrolled in any other research study, whether conducted by ICDDR,B or other organization, will be screened and enrolled subject to meeting the eligibility criteria. For Dukoral study that will be conducted in Shahrasti we will recruit only 2-5 years old children.